Electrically driven vibration welding devices have been capturing the market increasingly in the past years. A vibration welding system of the vibration welding device, especially an oscillating head, is commonly driven electrically. In contrast thereto, advancing systems of the vibration welding device were operated for a long time hydraulically or rarely pneumatically. The term advancing system comprises herein all movable elements of the vibration welding device which cause that a first work piece to be welded is moved towards or threaded into a second work piece to be welded, which is arranged at the oscillating head. For example, a lifting table as element of the advancing system of the vibration welding device has been driven hydraulically for years. The usage of electrical drives, as for example a spindle drive, was critical to impossible due to the vibrations or oscillations of the vibration welding device. This is especially founded in that both of the work pieces to be welded have to be pressed against each other during the welding process itself and thus a vibration is transferred to all elements of the vibration welding device, also to the spindle drive pressing both work pieces to be welded against each other. However, the spindle drive is not designed or suited for such vibration loads so that the durability of the spindle drive is shortened respectively.
Therefore, an electrical drive for the advancing system was developed years ago by the company BRANSON, which uses a traction means, namely chains or belts. An element of the advancing system to be moved, for example the lifting table, is herein coupled to the traction means firmly. The traction means itself is moved by an appropriate drive, for example by a servomotor or an asynchronous motor. In contrast to the spindle drive, the traction means are able to absorb the oscillations produced by the oscillating head of the vibration welding device and to oscillate therewith, if necessary. As the oscillations produced by the oscillating head are transferred inevitably also to a machine frame and to the lifting table of the vibration welding device, a co-vibration of the traction means is even more important.
Especially with respect to the welding process of a vibration welding device, a force is applied to the work pieces to be welded in that the advancing system, especially the lifting table, presses the first work piece to be welded against the second work piece to be welded, which is arranged at the oscillating head. In doing so, the traction means, thus the belt or the chain, is tensioned strongly in the area of the work pieces to be welded while the tension of the traction means is released on the side opposite to the work pieces to be welded.
A general disadvantage resulting from using traction means, especially in vibration welding devices, is that the traction means is elongated with time. Such an elongation has to be compensated usually manually to avoid malfunction or increased wear.
Particularly with respect to belts, especially toothed belts, as traction means, they have to be re-tensioned in a shorter operating time compared to chains as traction means. Also, the failure source at belts exists that the tension is adjusted too high or too low. Furthermore, and based on experience, the belts rapidly lose tension especially at the beginning, thus at their first use, and have to be re-tensioned quickly.
In case it is reacted to this initially large elongation with a respectively higher pretension, this results in a hard running of the device. Accordingly, a disproportional amount of energy is required for moving the advancing system. Furthermore, the wear in the used bearings is increased, which results in turn in a shortened durability of the advancing systems.
Similar problems exist when chains are used. They don't have to be re-tensioned after such a short operating time compared to belts but chains are also elongated over time due to wear.
Furthermore, and due to the releasing of the traction means on one side, there is the disadvantage that a driving by for example a drive gear does not take place reliably any longer. Further, it is also possible that the traction means jumps out of a guide and thus a proper operation of the vibration welding device is no longer ensured. For avoiding this, a manual re-adjustment of the traction means is being done for now.
It is thus the object of the present innovations to provide a traction means tensioner by means of which an automatic re-adjustment of the tension of the traction means, especially at the usage in welding devices like vibration welding devices, is possible. Furthermore, a corresponding production method for a respective traction means tensioner shall be given.